Nonvolatile memory (NVM) devices are able to retain stored data even when the power supply is interrupted. Non-volatile memory devices include flash devices which can be programmed using electrical signals. A NVM device, for example, includes a memory transistor and a select or access transistor in series. The memory transistor stores data programmed into the memory cell, while the access transistor selects the memory cell to be programmed or erased.
The memory transistor can be of various types. For example, the memory transistor may have a stacked gate structure having a control gate over a floating gate and a storage layer sandwiched between control and floating gates. During fabrication of the memory devices, we have observed that erosion of control gate occurs during processing, resulting in potential defects which cause reliability and yield issues.
The present disclosure is directed to a memory cell with improved reliability and the method of forming thereof.